Purpose :
To establish the resolution of measurements of the minimal distance between the central limit of the pigment epithelium and the inner limit of the retina (PIMD) as measured with spectral domain optical coherence tomography (SD-OCT) in a prospective clinical study.

Methods :
The optic nerve head was topographically recorded with SD-OCT (Topcon 3D, OCT-2000, protocol: 6x6 mm 3D disc cube). The minimal distance between the inner limit of the retina and the central limit of the pigment epithelium in a healthy eye was sampled 8 times and resolved in 500 angles. Additionally, the optic nerve head in glaucoma eyes were recorded at 2 separate visits with 3 measurements per visit. Each measurement was segmented 3 times.

Results :
The angular minimal distance was longer in the upper and the lower meridian and averaged 0.21 mm. An analysis of the consequence of the resolution demonstrated that the minimal relevant significant average difference at α= 0.05 and aiming for β= 0.2 was 0.11 change (mm)/Average (mm). Thus, a change of 2.4 x10-2 mm integrated over 2π is the detection limit at the selected statistical parameters. This corresponds to a local average change within one quadrant of 0.6 x10-2 mm. An analysis of variance of the measurements of glaucoma eyes imply that averaging over 3 measurements per visit results in sufficient precision.

Conclusions :
PIMD has the potential to be a useful variable for follow-up of glaucoma.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.